1. Field of the Invention
This invention relates to a grease composition having improved water resistance and to its method of preparation.
2. Description of Related Art
The use of polymers to impart desirable properties to greases is known and widely practiced by grease manufacturers (see E. N. Klemgard, Lubricating Greases (1937) and C. J. Boner, Manufacture and Application of Lubricating Greases (1954)). For example, oil soluble polymers have been used to increase the viscosity of the lubricating oil in the grease, thereby resulting in a grease having enhanced structural stability, reduced oil separation, and increased water resistance. However, although these benefits could be obtained without polymers using lubricating oils having high viscosity base-stocks, the resulting debit on low temperature mobility (i.e. pumpability) severely limits a non-polymer approach.
In addition, a recent publication (see G. D. Hussey, "Alternation of Grease Characteristics with New Generation Polymers", NLGI Spokesman, August 1987) compared the performance of commonly used polymers in various greases. However, none of the compositions mentioned in these references teach or suggest the water resistance grease composition described hereinafter.